This invention relates to antennas suited for use by aircraft or satellites for communications where a wide coverage conical beam is desired without the use of movable elements or electronic beam steering.
A variety of antennas have been designed for use at gigahertz frequencies. One such antenna design has a short back-fire cup-dipole driven element disposed a distance away from a center vertex of a concave cone shaped reflector. This antenna design utilizes a balun to match the driven element with a coaxial feed. The balun may be complicated to manufacture at such frequencies and provides matching characteristics that vary with temperature variations. Such an antenna is not capable of providing dual band operation where the two bands are separated by a substantial frequency difference, e.g. 20 GHz band and 45 GHz. Another antenna design is a conical helix antenna extending perpendicular from a planar reflector that provides limited bandwidth coverage and is likewise not capable of providing such dual band operation.
There exists a need for a single antenna that can provide a wide coverage conical beam and operate over two widely separated frequency bands.